Natural Radiation-Induced Damage in Quartz. I. Correlations Between Cathodoluminence Colors and Paramagnetic Defects

Abstract

Quartz grains from the McArthur River uranium deposit of the Athabasca Basin, Saskatchewan, are characterized by three distinct types of cathodoluminescence (CL): 1) halos surrounding U-and Th-bearing mineral inclusions, and 2) patches and 3) continuous rims along grain boundaries and fractures. These three types of CL have a constant width of ~35 to 45 m, consistent with the maximum depth of penetration of alpha particles, and therefore they record alpha-particle-induced radiation damage. Relative to the host grains, the radiation-damaged areas are characterized by pronounced but broad CL bands in the ultraviolet (~350 nm) and red (~620-650 nm) regions. Isochronal annealing experiments reveal that the ultraviolet CL persists to 500°C but is annealed out at 600°C, whereas the red CL persists to at least 800°C. Electron paramagnetic resonance (EPR) spectroscopy, including detailed measurements on saturation behavior and thermal properties, revealed six paramagnetic defects: one oxygen vacancy center (E 1 '), three silicon vacancy hole centers and two O 2 -peroxy centers. Spectral simulations confi rm the presence of these centers. Moreover, EPR spectra of HF-treated samples show that the silicon vacancy-hole centers and the peroxy centers are concentrated in the radiation-damaged rims and fractures. Center E 1 ' appears to occur throughout the quartz grains and is annealed out at ~500°C; it thus cannot be responsible for the ultraviolet or red CL. The silicon vacancy-hole centers are all annealed out between 550° and 600°C, similar to the annealing temperature of the ultraviolet CL. The peroxy centers are the only paramagnetic defects stable above 600°C, corresponding to the preservation of red CL in radiation-damaged areas at high temperatures. Therefore, the silicon vacancy-hole centers and the peroxy centers are probably responsible for the characteristic ultraviolet and red CL, respectively, associated with radiation-damaged halos, patches and rims in quartz.

Origin and significance of the yellow cathodoluminescence (CL) of quartz

“…The EPR spectra contain a characteristic oxygen-vacancy electron center E′ 1 (Mashkovtsev et al 2013) and an orthorhombic Fe 3+ center at the effective g value of 4.28 (Weil 1994;SivaRamaiah et al 2011). A closer look at the central magnetic region (Figs. 6b and 7) shows further multiple species of silicon-vacancy hole centers [e.g., superoxide and ozonide radicals such as B, B′, C, and C′; Botis et al (2005); Pan et al (2008] and an unknown center #3 with the effective g values of 2.008, 2.006, and 2.0045 (Mashkovtsev et al 1978). The agate from St. Egidien (AStE) is particularly interesting in that it contains abundant fiGure 2.…”

Refining late Quaternary plunge pool chronologies in Australia's monsoonal 'Top End'

“…However, zircon inclusions in quartz will have a strong effect on the internal dose rate of quartz that has been considered zero to this point. Furthermore, alpha emitters within quartz could change the OSL properties of the material with time by altering the structure of the crystal lattice and its point defects (Botis et al, 2005).…”

Characterization of oil shale residue and rejects from irati formation by electron paramagnetic resonance

“…S. Botis (2005) [10] employing the EPR data reveal the presence of six paramagnetic defects: one oxygen vacancy center (E1), three silicon vacancy hole centers O Figure 4 shows the XRD of retorted shale (RS) identifying the quartz as principal mineral, in accordance with the most intense peak and others, all indicated with hkl indexes [11], such result was also presented by Pimental et al (2006) [ 12]. In this analysis was possible to verify three more intense diffraction peaks associated with the kaolin group and three more intense diffraction peaks associated with pyrite, all indicated with label and hkl indexes [11].…”

“…In this analysis was possible to verify three more intense diffraction peaks associated with the kaolin group and three more intense diffraction peaks associated with pyrite, all indicated with label and hkl indexes [11]. The signal in the region g = 2.000 is (using the Cr 3+ pattern) 2.00043 which can be due to the unpaired electron in a vacancy of oxygen in which the electron occupies a silicon hybrid orbital sp 3 which is linked to three oxygen atoms in quartz sample as proposed by Botis S. (2005) [10]. …”